Colapinto took the chequered flag in Sunday's feature race in seventh place but was disqualified after the stewards received a report from the technical delegate.
This report indicated that the Williams Academy driver had failed to engage the start set-up procedure for the start of the race, something that the regulations demand all drivers must do for all formation lap starts as well as the race start.
The disqualification means Colapinto, who competes for MP Motorsport, loses the six points that he had scored, leaving him on 13 and in 13th in the championship standings. He also finished fourth in Saturday's sprint race.
On track, Hadjar was almost completely faultless around the Albert Park layout, leading the field to the chequered flag on Saturday and Sunday.
But his one error carried a severe price, when he pulled right at the start of the sprint race, forcing his Campos team-mate Pepe Marti into the side of Gabriel Bortoleto's Invicta entry, with the pair making heavy race-ending contact with the wall.
For this, Hadjar was handed a 10-second penalty, which dropped him to sixth.
Campos appealed this on Sunday morning and needed to present evidence that was "significant" and "a relevant new element".
Source: Autosport